In this Phase I, single-centre, open-label, adaptive, single-dose study at multiple dose levels, the relationship between dose and plasma concentration of orally administered V81444 to brain A2A RO was investigated in 6 healthy male volunteers. In addition, the effects of V81444 on regional brain activity and perfusion during tests of cognitive function, and the safety and tolerability of V81444 were assessed. For each subject, the study consisted of a screening visit, a baseline visit, a treatment period, and a safety follow-up visit. The dose of V81444 and timing of scans performed were defined in the protocol for the first 2 subjects only. The dose, nature and timings of assessments for subsequent subjects were determined based on review of emerging receptor binding, pharmacokinetic (PK), pharmacodynamic (PD) and safety information.